This invention relates to a method for treating a semiconductor wafer and in particular, but not exclusively, to what is known as planarisation.
Our Copending International Application No. PCT/GB93/01368 (published as WO94/01885) describes two methods of depositing a short-chain polymer on a wafer to form a generally planar layer:
1. A method of treating a semi-conductor wafer comprising, depositing a liquid short-chain polymer having the general formula Si.sub.x (OH).sub.y or Si.sub.x H.sub.y (OH).sub.z on the wafer to form a generally planar layer. PA1 2. A method of treating a semi-conductor wafer, including positioning the wafer in a chamber, introducing into the chamber silicon-containing gas or vapour and a compound, containing peroxide bonding, in vapour form, reacting the silicon-containing gas or vapour with the compound to form a short-chain polymer on the wafer to form a generally planar layer.
For the purpose of the description that follows wherein, these two methods will be referred to as "a method of the type described".
With the method of the type described the polymer will be in liquid form, at least to the extent that it is capable of a degree of self-levelling and, as is noted in Application No. PCT/GB93/01368, the water in the layer has to be removed at least partially, by heating. In order to prevent cracking, once a quantity of the water had been removed, a relatively thick capping layer was deposited prior to heating with the intention of providing physical stability for the polymer layer. Whilst this is advantageous it has not proved entirely successful as careful control of the process is required.